Electroluminescent-photoluminescent-photoresponsive apparatus



March 17, 1964 J. E. JOHNSON 3,125,681

ELECTROLUMINESCENT-PHOTOLUMINESCENT-PHOTORESPONSIVE APPARATUS FiledMarch 22, 1962 WHNESSES 'YINVENTOR Joseph E. Johnson United StatesPatent 3,125,681 ELECTROLUMINESCENT-PHOTOLUMINESCENT- PHOTORESPONSIVEAPPARATUS Joseph E. Johnson, Churchill Boro, Pa., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a

corporation of Pennsylvania Filed Mar. 22, 1962, Ser. No. 181,597 PClaims. (Cl. 250-413) The present invention relates to coincidenceswitching apparatus, and more particularly toelectroluminescent-photoresponsive coincidence switching apparatus.

In information display systems where a matrix of rows and columns areutilized to distribute the desired information, the problem arises ofactivating the selected element or elements of the matrix withoutactivating nonselected elements. Thus, if we have a matrix of X rows andY columns of elements, and if it is desired to activate the elements ofthe X, row and the Y, column, an electrical signal must be supplied tothe X, row and Y, column. However, the activating signals must beapplied in such a manner that the element X Y for example, or otherneighboring elements are not also activated at the same time. Theproblem is particularly acute in electroluminescent screen displayapparatus where present methods of using diode or ionic switches do notprovide the required degree of discrimination, but rather give a sidelighting eifect around the element desired to be illuminated, in that,the necessary isolation between rows and columns of elements is notprovided by the use of such switching devices.

It is therefore an object of the present invention to provide new andimproved switching apparatus which provides the desired degree ofisolation between rows and columns of a matrix.

It is a further object of the present invention to provide a new andimproved information display matrix which provides for the selection ofthe desired element without activating nondesired elements.

It is a further object of the present invention to provide new andimproved information modulating apparatus in which a modulating functionmay be provided without interference with other elements of an array.

Broadly, the present invention provides information modulating andswitching apparatus, wherein: photoresponsive elements are activated toprovide the switching or modulating function in response to thecoincidence of excitation of electroluminescent and photoluminescentelements.

These and other objects will become more apparent when considered inview of the following specification and drawings, in which:

FIG. 1 is a side view of one element of the present invention;

FIG. 2 is a top view of the matrix of the present invention; and

FIG. 3 is a section view of the matrix arrangement at the section lineIIIIlI, FIG. 2.

Referring to FIG. 1, a three element switching device with isolationbetween the input and output circuits is shown. The fabrication of thedevice of FIG. 1 may be such that the base plate 2 is a conductingmaterial such as aluminum. Upon the base plate 2 is sprayed anelectroluminescent layer EL, which may comprise a phosphor such as boronnitride. A boron nitride phosphor which emits an ultraviolet whenexcited by varying electric field is shown in US. Patent No. 2,921,218,issued on January 12, 1960. Onto the electroluminescent layer EL isapplied a transparent conducting layer of, for example, aluminum orgold. This layer 4 may be semitransparent, but must pass ultravioletlight from the electroluminescent layer EL. To the base plate 2 is3,125,681 Patented Mar. 17, 1964 "ice soldered the terminal 6, and tothe conducting layer 4 is soldered the terminal 8. By the application ofan alternating potential across the terminals 6 and 8, the electroluminescent layer EL will luminesce and depending upon the phosphorused will radiate light of a particular wavelength, for example as inthe present case, emission will be in the ultraviolet range.

The transparent insulating layer 10 is then sprayed over the conductinglayer 4. The insulating material is transparent and may, for example, bea polyvinyl chloride acetate plastic. Next, a transparent conductingstrip 12, similar to the conducting layer 4, is applied to theinsulating layer 10. A photoluminescent layer PL is then applied ontothe conducting layer 12. The photoluminescent layer PL may, for example,be a phosphor material such as cadmium sulfide, which has thecharacteristic that it radiates light in all directions when it receiveslight in the blue or ultraviolet range from the electroluminescent layerEL. The light emitted from the photoluminescent layer PL is generally ofa lower energy level than the light emitted from the electroluminescentlayer EL, and thus is generally of a longer wavelength. To thephotoluminescent layer PL is applied the transparent conducting layer14, which may, for example, be of gold or aluminum. Contacts 16 and 18are soldered to the conducting layers 12 and 14, respectively. Thephosphor of the photoluminescent layer PL has such a characteristic thatif a direct current of sufficient voltage is applied to terminals 16 and18 no light will be radiated from the photoluminescent layer when itreceives light from the electroluminescent layer EL. The charge quenchtype of phosphor is such that when a direct electric field of sutlicientmagnitude is applied across the phosphor no light will be radiatedtherefrom. Thus, whether the photoluminescent layer PL radiates light ornot may be controlled by an electric field applied across the terminals16 and 13. A single-crystal cadmium sulfide having the desiredphotoluminescent characteristics is described in the article Control ofLuminescence by Charge Extnaction, by Daniel, Schwartz, Lasser andHershinger, Physical Review, September l, 1958, pp. 1240-44.

To the conducting layer 14 is bonded a photoresponsive element PR. Thephotoresponsive element PR may, for example, comprise a well knowndevice such as a silicon or germanium photo diode which changesconductive states in response to light of the wavelength emitted by thephotoluminescent layer PL. The terminal 20 is soldered to the top of thephotoresponsive element PR. Thus, an output circuit is provided betweenthe terminals 18 and 20, that is, across the photoresponsive element PR.Characteristics of the photoresponsive element PR are such that if thephotoluminescent layer PL emits light through the transparent layer 14to the photoresponsive element PR, the photoresponsive element PR willbe in its conducting or low impedance state so that the switching actionoccurs between the terminals 18 and 21 If no light is emitted from thephotoluminescent element PL, then the photoresponsive element PR remainsin its high impedance or low conductivity state and provides an opencircuit between the terminals 18 and 20.

In order to provide the switching operation between the terminals 18 and20 of the photoresponsive element PR, there must be a coincidence ofexcitation potential applied to the electroluminescent layer EL acrossthe terminals 6 and 8, and also no biasing current should be applied tothe terminals 16 and 18 of the photoluminescent layer PL. Therefore, ifswitching action is desired across the terminals 18 and 20, anexcitation signal is applied to the terminals 6 and 8 which causes theelectroluminescent element EL to emit light of an ultra- 3 violetwavelength which is transmitted through the transparent conducting layer4, the transparent insulating layer It) and the transparent conductinglayer 12 to the photoluminescent layer PL. With no bias applied acrossthe terminals 16 and 18, the photoluminescent layer PL will emit lightof a longer wavelength which will be transmitted through the transparentconducting layer 14 to the photoresponsive element PR. Upon receipt ofthe light emitted from the photoluminescent layer PL, thephotoresponsive layer PR will change from its low conducting state toits high conducting state to provide a low impedance circuit orswitching action through the terminals 18 and 20. The switchingoperation then may be used to activate external circuitry as desired. Itshould be noted that by applying a biasing signal across terminals 16and 18 of less than quenching strength, the output appearing across theterminals 18 and 20 may be modulated in accordance with the biasingsignal applied to the terminals 16 and 18; thus providing less than theswitching action at the output terminals 18 and 20. Also, the excitingsignals applied to terminals 6 and 8 may be controlled to vary theoutput appearing at the terminals 18 and 20. However, for normalswitching action the coincidence of the conditions described above musttake place in order to provide the switching function and isolationbetween neighboring elements of a matrix of such elements as will nextbe explained below.

In FIGS. 2 and 3, a matrix of rows and columns that can be used as aninformation display array are shown. Onto the metal base plate 2, whichmay for example be aluminum, are sprayed strips EL, EL, etc. anelectroluminescent phosphor which for example may be boron nitride. Thestrips EL, EL, etc. of electroluminescent material form the rows of thematrix. Next, the transparent conducting strips 4, 4, etc. are appliedto each of electroluminescent strips EL, EL, respectively. The terminal6 is soldered to the base plate 2. The terminals 8, 8, etc. areconnected to the conducting strips 4, 4, etc. respectively, to providethe row terminations. An insulating layer, which for example may be apolyvinyl chloride acetate plastic, is then sprayed as a filler betweenthe electroluminescent elements EL, EL, etc. the conducting strips 4,4,etc. and the base plate 2. Next, transparent conducting strips 12, 12,which may be of gold or aluminum, are applied at right angles to theelectroluminescent strips EL, EL, etc. over the conducting strips 12,12', etc. are applied strips PL, PL, etc. of photoluminescent materialsuch as cadmium sulfide, with the photoluminescent strips PL, PL formingthe columns of the matrix. The overlapping sections of theelectroluminescent and photoluminescent strips thus form active areas ofthe matrix. Other conducting strips 14, 14, etc. are applied to the topsof the photoluminescent strips PL, PL, etc., respectively. Terminals 16,16, etc. are soldered to the conducting strips 12, 12, etc.,respectively, and terminals 18, 18, etc. are soldered to the conductingstrips 14, 14, etc. to provide column termination for the matrix. Overeach of the active areas at the intersection of the electroluminescentand photoluminescent strips, photoresponsive elements PR11, PR12, PR21,PR22, etc. are fixed. The photoresponsive elements may be well knowndevices such as silicon photo diodes. A conducting layer 22 is providedto hold the individual photoresponsive elements PRll, PRIZ, PRZl, PR22,etc. in place. The conducting layer 22 may for example be an epoxy resinin which particles are suspended. Output terminals Ztt, 20', etc. arethen soldered to each of the photoresponsive elements PRII, PRIZ, etc.with the output circuit being provided between the terminals 18, 18,etc. and the terminals 20, 26', etc. of the particular photoresponsiveelement PR.

Thus, if it is desired to provide the switching action at the activearea of the matrix defined by the photoresponsive element PRZZ, anexciting signal would be applied across the terminals 6 and 8, thuscausing the elecltroluminescent strip to radiate ultraviolet light atthe active area associated with the photoresponsive element PR22. Inorder that the photoluminescent material associated with the active arearadiate light in response to the ultraviolet light from theelectroluminescent material, no bias potential should be applied to theterminals l6 and 18 which are connected across the active area of thephotoluminescent material associated with the photoresponsive elementPR22. If no bias potential is provided across the terminals 16 and 18,the photoresponsive area will radiate light of a longer wavelength thanthat radiated by the electroluminescent area. When the light from thephotoluminescent area is received by the photoresponsive element PRZZ,the element will change from a low to a high conducting state, thuscompleting an output circuit between the terminals 18' and 20. Theswitching action appearing across the terminals 18 and 20 then may beused in external circuitry, for example, to energize anelectroluminescent cell of a screen matrix.

Although the present invention has been described with a certain degreeof particularity, it should be understood that the present disclosurehas been made only by way of example and that numerous changes in thedetails of fabrication and the combination and arrangement of elementsand materials may be resorted to without departing from the scope andspirit of the present invention.

I claim as my invention:

1. In switching apparatus operative with exciting sig nals andmodulating signals, the combination of: electroluminescent meanscomprising an electroluminescent phosphor material, suchelectroluminescent means being operative to emit light when saidexciting signals are applied thereto; photoluminescent means comprisinga photoluminescent phosphor disposed in physical relationship to saidelectroluminescent means to receive li ht therefrom, saidphotoluminescent means being operative to emit light in response to thereception of light from said electroluminescent means, saidphotoluminescent means further being operative to emit light inproportion to said modulating signals applied thereto; andphotoresponsive means disposed in physical relationship to receive lightfrom said photoluminescent means and being responsive thereto but beingunresponsive to light from said electroluminescent means, saidphotoresponsive means being operative to change conductive states inresponse only to light received from said photoluminescent means.

2. In switching apparatus operative with exciting signals and biasingsignals, the combination of: electroluminescent means comprising anelectroluminescent phosphor material, such electroluminescent meansbeing operative to emit light of a first wavelength when said excitingsignals are applied thereto; photoluminescent means comprising aphotoluminescent phosphor disposed in physical relationship to saidelectroluminescent means to receive light of said first wavelengththerefrom, said photoluminescent means being operative to emit light ofa second wavelength in response to the reception of light of said firstwavelength from said electroluminescent means, said photoluminescentmeans further being operative to not emit light when said biasingsignals are applied thereto; and photoresponsive means disposed inphysical relationship to receive light of said second wavelength fromsaid photoluminescent means and being responsive thereto but beingunresponsive to light of said first wavelength from saidelectroluminescent means, said photoresponsive means being operative tochange from a low conductive state to a high conductive state only whenlight is received from said photoluminescent means.

3. In switching apparatus operative with exciting signals and modulatingsignals, the combination of: an electroluminescent device comprising anelectroluminescent phosphor material, said electroluminescent devicebeing operative to emit light of a first wavelength when said excitingsignals are applied thereto; a photoluminescent device comprising aphotoluminescent phosphor disposed in physical relationship to saidelectroluminescent device to receive light of said first wavelengththerefrom, said photoluminescent device being operative to emit light ofa second wavelength in response to the reception of light of said firstwavelength from said electroluminescent device, said photoluminescentdevice further being operative to emit light in proportion to saidmodulating signals applied thereto; and a photoresponsive devicedisposed in physical relationship to receive light of said secondwavelength from said photoluminescent device and being responsivethereto but being unresponsive to light of said first wavelength fromsaid electroluminescent device, said photoresponsive device beingoperative to provide a modulated output function by changing conductivestates in response to the modulating signals to said photoluminescentdevice.

4. In coincidence switching apparatus operative with exciting signalsand biasing signals, the combination of: an electroluminescent devicecomprising an electroluminescent phosphor material, saidelectroluminescent device being operative to emit light of a firstwavelength when said exciting signals are applied thereto; aphotoluminescent device comprising a photoluminescent phosphor disposedin physical relationship to said electroluminescent device to receivelight of said first wavelengh therefrom, said photoluminescent devicebeing operative to emit light of a second wavelength in response to thereception of light of said first wavelength from said electroluminescentdevice, said photoluminescent device further being operative to not emitlight when said biasing signals are applied thereto; and aphotoresponsive device in physical relationship to receive light of saidsecond wavelength from said photoluminescent device and being responsivethereto but being unresponsive to light of said first wavelength fromsaid electroluminescent device, said photoresponsive device beingoperative to change from a low conductive state to a high conductivestate on the coincidence of the application of exciting signals to saidelectroluminescent device and no application of biassing signals to saidphotoluminescent device.

5. In coincidence switching apparatus operative with exciting signalsand biasing signals, the combination of: electroluminescent meansoperative to emit light of ultraviolet wavelengths when said excitingsignals are applied thereto; photoluminescent means disposed in physicalrelationship to said electroluminescent means to receive lighttherefrom, said photoluminescent device being operative to emit light oflonger wavelengths than said electroluminescent device in response tothe reception of light of said ultraviolet wavelengths from saidelectroluminescent means, said photoluminescent means further beingoperative to not emit light when said biasing signals are appliedthereto; and photoresponsive means disposed in physical relationship toreceive light from said photoluminescent means and being responsivethereto but being unresponsive to light of said ultraviolet wavelengthsfrom said electroluminescent means, said photoresponsive means beingoperative to change from a low conductive state to a high conductivestate on the coincidence of the application of exciting signals to saidelectroluminescent means and no application of baising signals to saidphotoluminescent means.

6. In coincidence switching apparatus operative with exciting signalsand biasing signals, the combination of: an electroluminescent devicecomprising an electroluminescent phosphor material, saidelectroluminescent device being operative to emit light of apredetermined wavelength when said exciting signals are applied thereto;a photoluminescent device comprising a photoluminescent phosphordisposed in physical relationship to said electroluminescent device toreceive light of said predetermined wavelength therefrom, saidphotoluminescent device being operative to emit light of a wavelengthlonger than said predetermined wavelength in response to the receptionof light of said predetermined wavelength from said electroluminescentdevice, said photoluminescent device further being operative to not emitlight when said biasing signals are applied thereto; and aphotoresponsive device disposed in physical relationship to receivelight of said longer than predetermined wavelength from saidphotoluminescent device and being responsive thereto but beingunresponsive to light of said predetermined wave length from saidelectroluminescent device, said photoresponsive device being operativeto change from a low conductive state to a high conductive state on thecoincidence of the application of exciting signals to saidelectroluminescent device and no application of biasing signals to saidphotoluminescent device.

7. In a coincidence switching matrix of rows and columns forming activeareas and operative with exciting signals and biasing signals, thecombination of: a plurality of strips of electroluminescent materialdisposed in a plane to form the columns of said matrix; a plurality ofstrips of photoluminescent material disposed in a plane with respect tosaid strips of electroluminescent material to form the rows of saidmatrix, with the overlapping sections of said strips forming the activeareas of said matrix, said electroluminescent material being responsiveto emit light of a first wavelength from the associated active area inresponse to said exciting signals being applied across the active areaof said electroluminescent material, said photoluminescent materialbeing responsive at the associated active area to emit light of a secondwavelength upon reception of light of said first wavelength from theassociated active area of said electroluminescent material, saidphotoluminescent material further being operative not to emit light ifsaid biasing signals are applied to the associated active area; and aplurality of photoresponsive elements disposed at each active areaadjacent said strips of photoresponsive material so that said elementsmay receive light of said second wavelength from said photoresponsivematerial and are responsive thereto but are unresponsive to light ofsaid first wavelength from said electroluminescent material, saidphotoresponsive elements being operative to provide a switching actionat a desired active area of said matrix by changing from a low to a highconducting state in response to the coincidence of exciting signalsbeing applied across the associated active area of saidelectroluminescent material and no biasing signals being applied acrossthe associated active area of said photoluminescent material.

8. In a coincidence switching matrix of rows and columns forming activeareas and operative with exciting signals and biasing signals, thecombination of: a plurality of electroluminescent strips disposed in aplane to form the columns of said matrix; a plurality ofphotoluminescent strips disposed in a plane with respect to saidelectroluminescent strips to form the rows of said matrix, with theoverlapping sections of said strips forming the active areas of saidmatrix, said electroluminescent strips being responsive to emit lightfrom the associated active area in response to said exciting signalsbeing applied across the active area of said electroluminescent strips,said photoluminescent strips being responsive at the associated activearea to emit light upon reception of light from the associated activearea of said electroluminescent strips, said photoluminescent stripsfurther being operative not to emit light if said biasing signals areapplied to the associated active area; and a plurality ofphotoresponsive elements disposed at each active area adjacent saidphotoresponsive strips so that said elements may receive light from saidphotoresponsive strips and are responsive thereto but are unresponsiveto light from said electroluminescent strip, said photoresponsiveelements being operative to provide a switching action at a desiredactive area of said matrix by changing from a low to a high conductingstate in response to the coincidence of exciting signals being appliedacross the associated active area of said electroluminescent strips andno biasd ing signals being applied across the associated active area ofsaid photoluminescent strips.

9. In an information distributing matrix of rows and columns formingactive areas and operative with exciting signals and modulating signals,the combination of: a plurality of electroluminescent strips disposed ina plane to form the columns of said matrix; a plurality ofphotoluminescent strips disposed in a plane with respect to saidelectroluminescent strips to form the rows of said matrix, with theoverlapping sections of said strips forming the active areas of saidmatrix, said electroluminescent strips being responsive to emit lightfrom the associated active area in response to said exciting signalsbeing applied across the active area of said electroluminescent strips,said photoluminescent strips being responsive at the associated activearea to emit light upon reception of light from the associated activearea of said electroluminescent strips, said photolurninescent stripsfurther being operative to emit light in proportion to said modulatingsignals applied to the associated active area; and a plurality ofphotoresponsive elements disposed at each active area adjacent saidphotoresponsive strips so that said elements may receive light from saidphotoresponsive strips and are responsive thereto but are unresponsiveto light from said electroluminescent strips, said photoresponsiveelements being operative to provide a modulated output function at adesired active area of said matrix by changing conducting states inresponse to said exciting signals being applied across the associatedactive area of said electroluminescent material and said modulatingsignals being applied across the associated active area of saidphotoluminescent strips.

References Cited in the file of this patent UNITED STATES PATENTS2,835,822 Williams May 20, 1958 2,836,766 Halsted May 27, 1958 2,856,553Henisch Oct. 14, 1958 2,904,697 Halsted Sept. 15, 1959 3,070,702 MarkoDec. 25, 1962 OTHER REFERENCES Daniel et 211.: Physical Review, SecondSeries, vol. 111, No. 5, Sept. 1, 1958, pages 1240-1244.

7. IN A COINCIDENCE SWITCHING MATRIX OF ROWS AND COLUMNS FORMING ACTIVEAREAS AND OPERATIVE WITH EXCITING SIGNALS AND BIASING SIGNALS, THECOMBINATION OF: A PLURALITY OF STRIPS OF ELECTROLUMINESCENT MATERIALDISPOSED IN A PLANE TO FORM THE COLUMNS OF SAID MATRIX; A PLURALITY OFSTRIPS OF PHOTOLUMINESCENT MATERIAL DISPOSED IN A PLANE WITH RESPECT TOSAID STRIPS OF ELECTROLUMINESCENT MATERIAL TO FORM THE ROWS OF SAIDMATRIX, WITH THE OVERLAPPING SECTIONS OF SAID STRIPS FORMING THE ACTIVEAREAS OF SAID MATRIX SAID ELECTROLUMINESCENT MATERIAL BEING RESPONSIVETO EMIT LIGHT OF A FIRST WAVELENGTH FROM THE ASSOCIATED ACTIVE AREA INRESPONSE TO SAID EXCITING SIGNALS BEING APPLIED ACROSS THE ACTIVE AREAOF SAID ELECTROLUMINESCENT MATERIAL, SAID PHOTOLUMINESCENT MATERIALBEING RESPONSIVE AT THE ASSOCIATED ACTIVE AREA TO EMIT LIGHT OF A SECONDWAVELENGTH UPON RECEPTION OF LIGHT OF SAID FIRST WAVELENGTH FROM THEASSOCIATED ACTIVE AREA OF SAID ELECTROLUMINESCENT MATERIAL, SAIDPHOTOLUMINESCENT MATERIAL FURTHER BEING OPERATIVE NOT TO EMIT LIGHT IFSAID BIASING SIGNALS ARE APPLIED TO THE ASSOCIATED ACTIVE AREA; AND APLURALITY OF PHOTORESPONSIVE ELEMENTS DISPOSED AT EACH ACTIVE AREAADJACENT SAID STRIPS OF PHOTORESPONSIVE MATERIAL SO THAT SAID ELEMENTSMAY RECEIVE LIGHT OF SAID SECOND WAVELENGTH FROM SAID PHOTORESPONSIVEMATERIAL AND ARE RESPONSIVE THERETO BUT ARE UNRESPONSIVE TO LIGHT OFSAID FIRST WAVELENGTH FROM SAID ELECTROLUMINESCENT MATERIAL, SAIDPHOTORESPONSIVE ELEMENTS BEING OPERATIVE TO PROVIDE A SWITCHING ACTIONAT A DESIRED ACTIVE AREA OF SAID MATRIX BY CHANGING FROM A